1. Field of the Invention
The present invention relates to power-line-operated inverter-type power supplies with means for controllably adjusting the RMS magnitude of the inverter output voltage.
2. Description of Prior Art
Power-line-operated inverter-type power supplies are presently being used in a variety of applications. In particular, such power supplies are frequently being used for powering low-voltage incandescent lamps or similar loads.
When using such inverter-type power supplies in connection with powering low-voltage incandescent lamps, it is sometimes desirable to be able controllably to adjust the RMS magnitude of the output voltage, thereby providing for adjustment of the amount of light provided by the lamps. However, to provide cost-effectively for means to effect controllable adjustment of the RMS magnitude of the output of such power supplies is not as simple as it might initially appear.
Of course, to achieve such adjustment control, one might use a variable-ratio transformer (Variac) between the power line and the input of the power supply. However, the cost and complexities associated with such an approach is unacceptably high in most applications.
Or, one might consider the use of a Triac-type voltage control means mounted between the power line and the power supply. However, Triac-type voltage control means simply do not function properly with the kind of input characteristics normally associated with power-line-operated inverter-type power supplies.
Then there is the possibility of using an inverter-type power supply with a special input circuit that would permit the use of a Triac-type control means; which input circuit would then have to make the inverter power-input-characteristics appear substantially like a resistive load. Even so, however, there is the cost of the Triac-type control to consider.
The present invention represents yet another solution; which other solution is novel and substantially more cost-effective than that of using a Triac-type control means between the power line and the inverter input.